The present invention relates to an image forming apparatus based on an electrographic process.
Regarding image forming apparatuses based on the electrographic process, it is known that several types of chemical substances are released from the image forming apparatus when images are formed. Examples among the released chemical substances are such as ozone which is generated when the photoreceptor drum is charged and toner dusts which are generated when images are developed or fixed. In the past, for example, filters are installed to prevent such generated chemical substances from being released outside the image forming apparatus.
For example, in JP-A-2009-282455, an electric field generating and collecting component generates an electric field in the air of the exhaust air duct, which is located over the fuser assembly in the volatile chemical substance collecting apparatus of an electronic device. VOC (Volatile Organic Compounds) in the air is drawn to the surface of the electric field generating and collecting component and is collected by effect of the electric field.
In JP-A-2011-180235, an image forming apparatus includes a duct which is located near the fuser apparatus, and the duct has a collecting hole for collecting particulates generated by the heating roller in fuser apparatus. An exhaust fan, which causes an air current from the collecting hole to an outlet, is provided in an expanded portion of the duct, and a first filter is provided in the upstream of the exhaust fan. The first filter collects ultrafine particles (e.g. siloxane) generated by a rubber layer, which constitutes the fuser apparatus. A shutter is provided to fill a gap between the first filter and the expanded portion, and a control part of the image forming apparatus switches between a state that the shutter covers the first filter and another state that the shutter does not cover the first filter according to a predetermined initial burst conditions.
Furthermore, in JP-A-2011-180283, a deodorization apparatus of a complex image forming apparatus includes plural gas passages, located at a bottom of housing, through which the gas flows into the housing. Each gas passage is tubular-shaped and an inside diameter of the upper part of housing is smaller than an inside diameter of the bottom of housing, and an ozone decomposing filter, which includes catalytic decomposing of ozone, is provided at a surface of the inside diameter of the tubular shape. A waste liquid absorber is provided at the inside bottom of the housing, a deodorizing absorber is provided at the upper lid in the housing, and an exhaust outlet for the gas which passes between the waste liquid absorber and the deodorizing absorber is provided on a side surface of the housing.
A recently growing concern is that the image forming apparatus based on the electrographic process generates particles (e.g. UFP (Ultrafine Particle) each having a diameter of less than 100 nm, which are different from ozone and the like, as the worldwide environmental conservation awareness grows.
However, for example, if the volatile chemical substance collecting apparatus of an electronic device, which draws VOC to the surface of the electric field generating and collecting component and collects it as shown in JP-A-2009-282456, is added as a structure for collecting UFP, it becomes a complex structure.
And if the first filter which is capable of collecting particles is provided in the upstream of the exhaust fan in the image forming apparatus and exhaust air passes through the first filter as shown in JP-A-2009-282456, it decreases the exhaust efficiency and increase the temperature in the housing because the first filter increases resistance when the air flows. Therefore, an output of the exhaust fan has to be increased, which leads to a concern that it generates noise and increases its running cost.
Furthermore, if a plurality of dedicated deodorization apparatuses are provided like the complex image forming apparatus shown in JP-A-2011-180283 (e.g. two deodorization apparatuses are described in JP-A-2011-180283), the structure becomes complex and the cost of the apparatus increases.